Variable stiffness-energy consumption assembly type wet connection joint for steel concrete superposed beam

Abstract

The invention discloses a variable stiffness-energy consumption assembly type wet connection joint for a steel concrete superposed beam. The variable stiffness-energy consumption assembly type wet connection joint comprises a prefabricated concrete bridge deck, prestressed tendons, prestressed ducts, SMA bolts with holes, wet joints, an I-shaped steel beam, longitudinal steel bars, transverse steel bars, connecting bolts, connecting springs, protective nuts, end plates and SMA bolt holes. When the bridge deck deforms due to external loads such as vehicles, impact or earthquakes, a pre-pressing structure combined with a pressing-pulling stress area formed by the prestressed tendons in the bridge deck and the wet joints can counteract the influence of part of the external loads on the bridge deck, crack development of the bridge deck is restrained, and part of extrusion and collision energy is dissipated. And meanwhile, the SMA bolts in the wet joints are subjected to phase change along with the pre-pressure change of the pre-stressed tendons and the relative deformation effect among the bridge deck, the wet joints and the steel beams, and energy is further dissipated. The joint has the advantages of being simple in construction process, good in assembly performance, variable in joint energy consumption, variable in rigidity and detachable, and can be used in bridge engineering construction.

Description

Technical Field

[0001] This invention relates to a wet joint for steel-concrete composite beams with advantages such as prefabricated structure, variable stiffness-energy dissipation and self-resetting function, belonging to the field of bridge construction technology. Background Technology

[0002] In recent years, steel-concrete composite beams have been widely used. They fully utilize the compressive mechanical properties of reinforced concrete and the tensile mechanical properties of steel beams, and have advantages such as light weight, easy assembly and good spanning capacity, making them highly favored by the industry.

[0003] Steel-concrete composite beams are typically prefabricated, with both the steel beams and precast concrete slabs manufactured in factories and connected on-site via wet joints. Currently, wet joint filling materials are gradually shifting from traditional ordinary concrete to high-performance concrete materials such as ECC and UHPC to better control bridge deck crack development. Research on joint connection performance focuses on the development and application of novel connection joint methods, such as U-shaped and J-shaped rebar joints. However, current research and design concepts remain consistent with traditional ordinary concrete, failing to propose design parameters suitable for high-performance concrete materials, hindering the full realization of the mechanical properties of high-performance wet joint materials. Furthermore, the applicability and ease of construction of U-shaped and J-shaped rebar connections at joints in high-performance wet joints still present many challenges. In addition, neither traditional nor high-performance wet joints have considered the dynamic matching of stiffness and mechanical properties between the steel beams, concrete slabs, and wet joints. Therefore, the durability and safety of steel-concrete composite beams and their connection structures remain significant limiting factors for their widespread application.

[0004] To improve the durability and safety of steel-concrete composite beams, the main research directions of scholars currently include: (1) controlling the cracking of joints and concrete slabs through prestressing and structural design; (2) improving joint performance through new materials (such as UHPC, ECC, and SMA). At present, on the one hand, due to the geometric size limitations of the prestressed composite beam concrete slab, the application method and effectiveness of prestressed structural design in composite beam concrete slabs are questionable; on the other hand, conventional prestressed structural design may have adverse effects on the mechanical performance of high-performance wet joints, and the matching relationship between prestressed structural design and the performance of high-performance wet joints needs to be emphasized; in addition, due to the improvement of the disaster resistance toughness of engineering structures by the engineering and academic communities, the disaster resistance toughness and recoverability of steel-concrete composite beams and their wet joints have gradually become a focus of attention.

[0005] In view of this, this invention patent proposes a variable stiffness-energy dissipation prefabricated wet joint for steel-concrete composite beams. The prefabricated preloading method can control shrinkage cracks in precast bridge decks to a certain extent; the combination of unbonded construction and shape memory alloy can better utilize the performance of the wet joint and provide greater adjustability; the use of shape memory alloy at the wet joint enables variable stiffness and variable energy dissipation at the joint. Summary of the Invention

[0006] To address the challenges of achieving high-performance wet joints in steel-concrete composite beams, the susceptibility of precast bridge decks to cracking, and the limited stiffness, energy dissipation, and repositioning capabilities of wet joints, this invention proposes a variable stiffness-energy dissipation prefabricated wet joint for steel-concrete composite beams. This joint features a simple construction process, high energy dissipation capacity, stable energy dissipation, a certain degree of self-repositioning capability, and assemblability.

[0007] To achieve the above objectives, the present invention adopts the following technical solution.

[0008] This invention provides a variable stiffness-energy-dissipating prefabricated wet joint structure for a steel-concrete composite beam, comprising a precast concrete bridge deck 1, prestressed tendons 2, prestressed ducts 3, perforated SMA bolts 4, a wet joint 5, an I-beam 6, longitudinal reinforcement 7, transverse reinforcement 8, connecting bolts 9, connecting springs 10, protective nuts 11, an end plate 12, and SMA bolt holes 13. The assembly steps of this concrete composite beam are as follows: First, the precast concrete bridge deck 1 and the I-beam 6 are manufactured in sections at the factory, including the pre-reserved prestressed ducts 3, connecting bolts 9, connecting springs 10, and pre-reserved holes 13 for SMA bolts 4 at the wet joint 5 on the top plate of the I-beam 6. Then, the I-beam 6 with the connecting bolts 9, connecting springs 10, and pre-reserved holes 13 for SMA bolts 4, and the precast bridge deck 1 are transported to the site. After being hoisted and erected at the designated position on the I-beam 6, the precast bridge deck 1 is laid. Ensure that the transverse reinforcing bars 8 and the longitudinal reinforcing bars 7 bent into U-shapes on both sides of the precast bridge deck 1 are tied together to form a reinforcing cage that extends into the wet joint 5, connecting the precast bridge deck 1 and the wet joint 5. Then, threaded SMA bolts 4 are initially screwed into the protective nuts 11 with openings on both sides, and unbonded prestressing tendons 2 are inserted. Then, the unbonded prestressing tendons 2 with SMA bolts 4 and protective nuts 11 are inserted into the unbonded prestressing channels 3 of the precast bridge deck 1 on both adjacent sides, and the SMA bolts 4 are inserted into the bolt holes 13 and initially fixed in the end plate 12. Based on this, a wet joint construction template is set up, and wet joint 5 is poured on site. After the strength and elastic modulus of the high-performance concrete material in wet joint 5 meet the requirements, unbonded prestressed tendons 2 are tensioned and anchored on one or both sides. Then, the nuts at the end plate 12 are tightened and the protective nuts 11 are used to apply pre-tightening force to the SMA bolts 4, thus forming a variable stiffness-energy dissipation prefabricated wet joint for steel-concrete composite beams.

[0009] The aforementioned variable stiffness-energy-dissipating prefabricated wet joint for steel-concrete composite beams is characterized in that, when external loads such as vehicles, impacts, or earthquakes cause deformation of the bridge deck 1, the prestressing structure formed by the compression-tension prestressing zone of the prestressing tendons 2 within the bridge deck 1 and the wet joint 5 can offset part of the impact of the external load on the bridge deck 1, inhibit the development of cracks in the bridge deck 1, and dissipate some of the compressive impact energy. Simultaneously, the SMA bolts 4 within the wet joint 5 undergo a phase transition along with the changes in the prestressing pressure of the prestressing tendons 2 and the relative deformation between the bridge deck 1, the wet joint 5, and the steel beam 6, further dissipating energy. The SMA bolts 4 and protective nuts 11 provide anchorage for the unbonded prestressing tendons 2 passing through them, enabling the prestressing tendons 2 to be arranged along the entire length of the bridge. The energy dissipation mechanism of the SMA bolts 4 and the unbonded prestressing tendons 2 complement and work synergistically to dissipate energy. After unloading, the connecting spring 10 releases compressive potential energy, assisting the SMA bolts 4 in returning to their initial state through their shape memory effect, reducing residual structural displacement, thereby enabling the wet joint to have a self-resetting function. Furthermore, the connecting spring 10, SMA bolt 4, and prestressing tendon 2 assembly can provide different loading and unloading stiffnesses at the wet joint 5 during different stress stages of the bridge deck, realizing the variable stiffness function of the prefabricated wet joint node. Its specific functions and technical features are as follows.

[0010] 1. Combination of compression and tension prestressing to control bridge deck cracks: After the prestressing tendons 2 are tensioned, a compressive stress zone is formed in the precast bridge deck 1. At the same time, a tensile stress zone is formed in the wet joint 5 by means of the anchoring effect of the prestressing tendons 2 with the SMA bolts 4 and protective nuts 11 connected to them. When the bridge deck is subjected to load and undergoes relative deformation, the prestressing mode of the prestressing tendons 2 combined with compression and tension prestressing will be used to offset part of the stress and deformation of the bridge deck, inhibit the development of bridge deck cracks and dissipate some of the extrusion and collision energy.

[0011] 2. Shape Memory Alloy Shear Extrusion Energy Dissipation and Self-Resetting Function: The connecting spring 10 and prestressing tendon 2 provide initial preload to the SMA bolt 4, which is key to realizing the dual functions of energy dissipation and self-resetting of the SMA bolt 4. During the small deformation stage under vehicle load or the large deformation stage under earthquake or impact load, the SMA bolt 4, along with the preload change of the prestressing tendon 2 and the relative deformation between the bridge deck 1, wet joint 5, and steel beam 6, can undergo phase change to dissipate energy, reduce structural damage, and minimize residual displacement. After unloading, the connecting spring 10 assists the SMA bolt 4 in achieving self-resetting by releasing the stored compressive energy, returning it to its initial state.

[0012] 3. Unbonded structure + SMA structure synergistic energy dissipation: The unbonded prestressing tendon 2 and the SMA bolts 4 installed on it work together. The SMA bolts 4 and the protective nuts 11 provide a certain anchoring effect for the prestressing tendon 2, and assist the prestressing tendon 2 in playing a role in enhancing anchoring efficiency and controlling cracks. The prestressing tendon 2 provides the driving force for the SMA bolts 4 to play an excellent energy dissipation capacity and self-resetting function. At the same time, the complementary mechanism formed by the prestressing tendon 2 and the SMA bolts 4 can also reduce the amount of SMA bolts 4 and the connecting bolts 9 at the wet joint 5, thereby reducing the project cost.

[0013] The variable stiffness characteristics of the connecting spring 10 and SMA bolt 4, as well as the prestress of the prestressed tendon 2 after tensioning, can provide different loading and unloading stiffnesses in the bridge deck 1 and wet joint 5 at different stress stages, thereby achieving the balance and adjustability of the reset-energy dissipation function of the prefabricated wet joint. The corresponding loading stiffness and unloading stiffness can be adjusted by the number of connecting springs 10 and SMA bolts 4, as well as the preload of the prestressed tendon 2.

[0014] The final effective preload of the prestressing tendon 2 can be applied according to the realization of the elastic recovery and phase transformation energy dissipation functions of the SMA bolt 4. When the SMA bolt 4 needs to fully exert its energy dissipation capacity, the effective prestress provided by the prestressing tendon 2 to the SMA bolt 4 (the tensile stress of the SMA bolt 4 caused by the component of the effective preload of the prestressing tendon 2 along the SMA bolt 4, which is related to the angle between the prestressing duct 3 and the SMA bolt 4) should be higher than the initial phase transformation critical stress of the SMA bolt 4, but lower than the stress value corresponding to its maximum recoverable strain, so as to ensure that the SMA bolt 4 can trigger phase transformation energy dissipation under load without plastic damage. When the elastic recovery function of the SMA bolt 4 is required, the effective prestress provided by the prestressing tendon 2 to the SMA bolt 4 can be controlled to be 0.2 to 0.6 times the phase transformation critical stress of the SMA bolt 4.

[0015] The tensioning control stress of the prestressing tendon 2 is 30% to 60% of its ultimate strength to retain a safety reserve of prestress. The SMA bolt holes 13 on the I-beam 6 and the prestressing ducts 3 of the precast bridge deck 1 adopt an adjustable positioning structure. By changing the relative height difference between the reserved prestressing ducts 3 and the SMA bolt holes 4, the axial angle between the prestressing tendon 2 and the SMA bolt 4 can be adjusted, thereby dynamically controlling the effective preload at the SMA bolt 4 node to meet the needs of different prestressing reset and preloading functions and SMA bolt reset energy dissipation functions under different load conditions.

[0016] The number and stiffness of the connecting springs 10 must be set to ensure that the total parallel stiffness of the connecting springs 10 is within the range of 0.5 to 1.5 times the total parallel stiffness of the SMA bolts 4, so as to ensure that the SMA bolts 4 can enter different phase transformation stages based on their stiffness, and realize variable energy dissipation to adapt to different bridge deck load changes. In addition, the connecting springs 10 should have a certain amount of pre-compression, controlled at 1.5 to 3.0 times the tension expansion joint of the SMA bolts 4 and prestressed tendon 2 system, to ensure that when unloading, the connecting springs 10 can drive the SMA bolts 4 to return to the initial state through the change of expansion and contraction, without excessively constraining the phase transformation energy dissipation deformation of the SMA bolts 4, so that the node can realize the self-resetting function.

[0017] Compared with the prior art, the advantages of the present invention are as follows: (1) The combined compression-tension prestressing structure controls cracks in precast concrete bridge decks; (2) The application of SMA+ connecting springs helps wet joints to achieve variable stiffness, variable energy dissipation, and recoverability when subjected to external forces; (3) Unbonded structure + SMA structure, which is conducive to the performance and adjustability of nodes; Attached Figure Description

[0018] Figure 1 Side view of the variable stiffness-energy dissipation prefabricated wet joint for steel-concrete composite beams.

[0019] Figure 2 This is an assembly drawing for prefabricated bridge deck panels.

[0020] Figure 3 Diagram of variable stiffness-energy dissipation prefabricated wet joint for steel-concrete composite beams.

[0021] Figure 4 A schematic diagram of the assembly sequence for variable stiffness-energy dissipation prefabricated wet joints used in steel-concrete composite beams.

[0022] Figure 5 Left (right) side view of a variable stiffness-energy dissipation prefabricated wet joint for a steel-concrete composite beam.

[0023] In the diagram: 1: Precast concrete bridge deck, 2: Prestressed tendon, 3: Prestressed duct, 4: SMA bolt with hole, 5: Wet joint, 6: I-beam, 7: Transverse reinforcement, 8: Longitudinal reinforcement, 9: Connecting bolt, 10: Connecting spring, 11: Protective nuts with holes on both sides, 12: End plate, 13: Bolt hole. Detailed Implementation

[0024] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0025] like Figure 1 As shown, this example provides a variable stiffness-energy dissipation prefabricated wet joint structure for steel-concrete composite beams used in bridge construction, including a precast concrete bridge deck 1, prestressed tendons 2, prestressed ducts 3, perforated SMA bolts 4, wet joint 5, I-beam 6, longitudinal reinforcement 7, transverse reinforcement 8, connecting bolts 9, connecting springs 10, protective nuts 11, end plates 12, and SMA bolt holes 13.

[0026] like Figure 2 , Figure 5As shown, firstly, I-beams 6 with dimensions of 2390mm×600mm×16mm×30mm and precast bridge deck 1 are manufactured in sections at the factory. During manufacturing, 9.8 grade high-strength connecting bolts 9 and connecting springs 10 with a total stiffness of 120kN / mm are pre-welded to the flanges of the I-beams 6 where the wet joint 5 is located, and holes 13 for SMA bolts 4 are set. The diameter of the holes 13 is 20mm, and the inner wall is galvanized for rust prevention. The reinforcing cage connected to the wet joint 5 in the precast bridge deck 1 is composed of longitudinal reinforcing bars 7 and transverse reinforcing bars 8 tied together, and the intersections are tied with wire to form a double-layer reinforcing mesh. The longitudinal reinforcing bars 7 are HRB400 steel bars with a diameter of 8mm and a spacing of 60mm, and the transverse reinforcing bars 8 are HRB400 steel bars with a diameter of 6mm and a spacing of 70mm. Then, the I-beam 6 and precast bridge deck 1, equipped with connecting bolts 9, connecting springs 10, and reserved holes 13, are transported to the site, hoisted to the designated position, and assembled, with a spacing of 100mm between adjacent bridge decks 1. Threaded SMA bolts 4 with a diameter of 20mm and holes are initially screwed into protective nuts 11 through bolt holes 13. The relative height difference between the prestressing channel 3 and the hole of the SMA bolt 4 is 10mm, achieving an axial angle of 12°, thus increasing the preload of the SMA bolt 4 by 18%. The SMA bolt 4 is made of NiTiNb alloy, with a phase transformation critical stress set at 350MPa and a maximum recoverable stress of 650MPa. The exposed length of the lower end of the SMA bolt 4 is 160mm, and the exposed hole of the protective nut 11 must be aligned with the upper hole of the SMA bolt 4 and larger than the diameter of the prestressing tendon. Next, 1860-grade prestressing tendons with a diameter of 15.2 mm are passed through SMA bolts 4 and protective nuts 11. A traction device is used to ensure the prestressing tendons 2 are arranged along their entire length within the precast bridge deck 1. Furthermore, end plates 12 are screwed into the ends of SMA bolts 4 and secured with nuts. A pre-tightening force is provided to the SMA bolts 4 using connecting springs 10 and protective nuts 11. The pre-compression of connecting springs 10 is 8 mm, which is 2.5 times the designed expansion joint amount, ensuring a reset driving force of ≥8 kN for the joint. End plates 12 are made of Q235 steel plate with a thickness of 30 mm and are tightened to 200 N•m using a torque wrench to ensure a tight fit between the end plates 12 and the connecting springs 10. Subsequently, a wet joint construction formwork was erected, and high-performance concrete materials such as ECC and UHPC were poured at wet joint 5. After the concrete material at wet joint 5 reached the specified strength and modulus of elasticity, the prestressing tendons 2 were tensioned using a symmetrical tensioning method at both ends, with loading in three stages, each held for 5 minutes, until the final tension reached 45% of the ultimate stress, with a 55% safety reserve. Protective nuts 11 were then tightened simultaneously, applying a preload of 400 MPa. This resulted in a variable stiffness-energy-dissipating prefabricated wet joint structure for steel-concrete composite beams, achieving high-precision assembly and multi-functional joint performance for the steel-concrete composite beams.

[0027] The above are merely examples of the technical solutions of this invention, but the implementation of this invention is not limited to these examples. Without departing from the principles of this invention, those skilled in the art can make improvements to the specific implementations of this invention, and all such modifications are within the scope of protection of this invention. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A variable stiffness-energy-dissipating prefabricated wet joint for steel-concrete composite beams, characterized in that: It includes precast concrete bridge deck (1) and I-beams (6); The concrete bridge deck (1) and the I-beam (6) are prefabricated in sections in the factory. The I-beam (6) is hoisted to the designated position and the concrete bridge deck (1) is laid on the I-beam (6). Wet joints (5) are provided between each concrete bridge deck (1). The wet joints (5) include connecting bolts (9), connecting springs (10), SMA bolts (4) and reserved holes (13). The concrete bridge deck (1) includes a pre-stressed duct (3), longitudinal steel bars (7), and transverse steel bars (8); concrete is poured after the longitudinal steel bars (7) and transverse steel bars (8) are tied and fixed together with the pre-stressed duct (3); the steel cage formed by the transverse steel bars (8) and the longitudinal steel bars (7) bent into U-shapes on both sides extends into the wet joint (5) to connect the precast bridge deck (1) and the wet joint (5). The threaded SMA bolts (4) are initially screwed into the protective nuts (11) with openings on both sides, and then inserted into the unbonded prestressing tendons (2); the unbonded prestressing tendons (2) with SMA bolts (4) and protective nuts (11) are inserted into the unbonded prestressing ducts (3) of the adjacent precast bridge decks (1), and the SMA bolts (4) are inserted into the bolt holes (13) and initially fixed in the end plates (12); the I-beams (6) and the wet joints (5) are connected by a channel. The joint is connected by multiple parallel connecting bolts (9); a connecting spring (10) is provided between the end plate (12) and the I-beam (6); a wet joint construction template is set up and the wet joint (5) is poured. After the strength and elastic modulus of the high-performance concrete material in the wet joint (5) meet the requirements, the unbonded prestressed tendons (2) are tensioned on one side or both sides and anchored. Then the nuts at the end plate (12) are tightened and the protective nuts (11) are used to apply pre-tightening force to the SMA bolts (4).

2. The variable stiffness-energy dissipation prefabricated wet joint for steel-concrete composite beams according to claim 1, characterized in that: When the bridge deck (1) is deformed by external loads such as vehicles, impacts or earthquakes, the prestressed structure formed by the prestressed tendons (2) in the bridge deck (1) and wet joint (5) can offset part of the influence of external loads on the bridge deck (1), suppress the development of cracks in the bridge deck (1) and dissipate part of the extrusion collision energy; the SMA bolts (4) in the wet joint (5) undergo phase transformation with the change of prestressing force of the prestressed tendons (2) and the relative deformation between the bridge deck (1), wet joint (5) and steel beam (6), further dissipating energy.

3. The variable stiffness-energy dissipation prefabricated wet joint for steel-concrete composite beams according to claim 1, characterized in that: The SMA bolt (4) and protective nut (11) provide anchorage for the unbonded prestressed tendon (2) passing through it, enabling the prestressed tendon to be arranged along the entire length of the bridge. The energy dissipation mechanism of the SMA bolt (4) and the unbonded prestressed tendon (2) complement each other and work together to dissipate energy. After unloading, the connecting spring (10) releases the compressive potential energy, assisting the SMA bolt (4) to recover to its initial state by virtue of its shape memory effect, reducing the residual displacement of the structure, thereby enabling the wet joint to have a self-resetting function. The connecting spring (10), SMA bolt (4) and prestressed tendon (2) assembly provide different loading and unloading stiffness at the wet joint (5) at different stress stages of the bridge deck, realizing the variable stiffness function of the prefabricated wet joint. Its specific functions and technical characteristics are as follows: 1) Combination of compression and tension prestressing to control bridge deck cracks: After tensioning the prestressing tendons (2), a compressive stress zone is formed in the precast bridge deck (1). At the same time, the prestressing tendons (2) form a tensile stress zone in the wet joint (5) by means of the anchoring effect of the SMA bolts (4) and protective nuts (11) connected to them. When the bridge deck is subjected to load and undergoes relative deformation, the prestressing mode of the combination of compression and tension prestressing of the prestressing tendons (2) will be used to offset part of the stress and deformation of the bridge deck, suppress the development of bridge deck cracks and dissipate part of the extrusion collision energy. 2) Shape memory alloy shear extrusion energy dissipation and self-resetting function: The connecting spring (10) and prestressing tendon (2) provide initial pretension for the SMA bolt (4), which is the key to realizing the dual functions of energy dissipation and self-resetting of the SMA bolt (4); During the small deformation stage of vehicle load or the large deformation stage under earthquake and impact load, the SMA bolt (4) can dissipate energy through phase change along with the prestressing change of the prestressing tendon (2) and the relative deformation between the bridge deck (1), wet joint (5) and steel beam (6), thereby reducing structural damage and reducing residual displacement; After unloading, the connecting spring (10) releases the stored compression energy to assist the SMA bolt (4) in realizing the self-resetting function and returning to the initial state; 3) Unbonded structure and SMA structure work together to dissipate energy: The unbonded prestressed tendon (2) structure works together with the SMA bolts (4) set on it. The SMA bolts (4) and protective nuts (11) provide anchorage for the prestressed tendon (2) and assist the prestressed tendon (2) in playing the role of anchorage enhancement and crack control. The prestressed tendon (2) provides driving force for the SMA bolts (4) to play the role of excellent energy dissipation capacity and self-resetting function. The complementary mechanism formed by the prestressed tendon (2) and the SMA bolts (4) can reduce the amount of SMA bolts (4) and connecting bolts (9) at the wet joint (5) and reduce the project cost.

4. The variable stiffness-energy dissipation prefabricated wet joint for steel-concrete composite beams according to claim 1, characterized in that: The variable stiffness characteristics of the connecting spring (10) and SMA bolt (4) and the prestress of the tensioned prestressed tendon (2) provide different loading and unloading stiffness in the bridge deck (1) and wet joint (5) at different stress stages, so as to realize the balance and adjustability of the reset-energy dissipation function of the prefabricated wet joint. The corresponding loading stiffness and unloading stiffness are adjusted by the number of connecting spring (10) and SMA bolt (4) and the pre-tightening force of the prestressed tendon (2).

5. The variable stiffness-energy dissipation prefabricated wet joint for steel-concrete composite beams according to claim 1, characterized in that: The final effective preload of the prestressing tendon (2) is applied according to the realization of the elastic recovery and phase transformation energy dissipation function of the SMA bolt (4). When the SMA bolt (4) needs to fully utilize its energy dissipation capacity, the effective preload provided by the prestressing tendon (2) to the SMA bolt (4) should be higher than the initial phase transformation critical stress of the SMA bolt (4), but lower than the stress value corresponding to its maximum recoverable strain, so as to ensure that the SMA bolt (4) can trigger phase transformation energy dissipation under load without plastic damage. When the elastic recovery function of the SMA bolt (4) is required, the effective preload provided by the prestressing tendon (2) to the SMA bolt (4) can be controlled to be 0.2 to 0.6 times the phase transformation critical stress of the SMA bolt (4).

6. The variable stiffness-energy dissipation prefabricated wet joint for steel-concrete composite beams according to claim 1, characterized in that: The tensile stress in the SMA bolt (4) caused by the component of the effective prestressing force of the prestressing tendon (2) along the SMA bolt (4) is related to the angle between the prestressing duct (3) and the SMA bolt (4).

7. A variable stiffness-energy dissipation prefabricated wet joint for steel-concrete composite beams according to claim 1, characterized in that: The tensioning control stress of the prestressed tendon (2) is 30% to 60% of the ultimate strength to retain the safety reserve of prestress. The SMA bolt hole (13) on the I-beam (6) and the prestressed channel (3) of the precast bridge deck (1) adopt an adjustable positioning structure. By changing the relative height difference between the reserved prestressed channel (3) and the SMA bolt (4) hole, the axial angle between the prestressed tendon (2) and the SMA bolt (4) is adjusted, thereby dynamically controlling the effective pre-tightening force at the SMA bolt (4) node to meet the needs of different prestress reset and pre-stressing functions and SMA bolt (4) reset energy dissipation functions under different load conditions.

8. The variable stiffness-energy dissipation prefabricated wet joint for steel-concrete composite beams according to claim 1, characterized in that: The quantity and stiffness of the connecting springs (10) must be set to ensure that the total parallel stiffness of the connecting springs (10) is within 0.5 to 1.5 times the total parallel stiffness of the SMA bolts (4), so as to ensure that the SMA bolts (4) can enter different phase transformation stages based on their stiffness, and realize variable energy consumption to adapt to different bridge deck load changes; the connecting springs (10) have a pre-compression amount, which is controlled by 1.5 to 3.0 times the tension expansion joint amount of the SMA bolts (4) and prestressed tendons (2) system, so as to ensure that when unloading, the connecting springs (10) can drive the SMA bolts (4) to return to the initial state through the change of expansion and contraction amount, without excessively constraining the phase transformation energy consumption deformation of the SMA bolts (4), so that the node realizes the self-resetting function.

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